Kevin
Thanks for the explanation this all makes
sense now.
I’ll be playing later today and I’ll
post my findings.
Thanks once again for the pointers
Rob
-----Original Message-----
From:
[email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Kevin Custer
Sent: 03 June 2005 23:27
To:
[email protected]
Subject: Re: [Repeater-Builder]
Help with Wacom WP-639 Duplexer
Hi Rob,
Rob Martin wrote:
Kevin
Thanks
for tips, I had download the VHF tune up PDF but not the other pdf.
I was
surprised he had such problems as I had bought two sets of duplexers, one was a
DB products until which he said failed as they had 2 notches and the second set
being the wacom which he said wouldn’t tune down.
When you
say tune them upside down could you explain a little further for me as this is
my first attempt to put a repeater on air.
The Wacom WP-639 is a BpBr design, meaning Band Pass - Band
Reject. The duplexer is specifically built to pass a particular
frequency, and reject another. The components of the duplexer determine
if the notch falls above or below the pass frequency. In the
case of a regular duplexer, one side
is HPLR (high pass low reject) and the other is LPHR (low pass high
reject). Many times, from the factory, a duplexer has its ports marked
"Transmitter" and "Receiver", but those terms are
meaningless unless the duplexer is used in the same band segment as it was tuned
from the factory. Let's look at it this way, say you have a repeater on
146.625 minus 600 kHz. This repeater would be HPLR on the transmitter and
LPHR on the receiver. Follow me?
Now, lets look at 147.195 plus 600 kHz. This repeater would be LPHR on
the transmitter and HPLR on the receiver, or exactly opposite. This means
if you bought a duplexer that was originally built for 146.625 - and retuned it
to 147.195 +, you'd have to ignore the references to port identification
"TX" and "RX" and connect them inversely. If you tried
to tune the HPLR to LPHR, the duplexer wouldn't tune; it would likely be more
lossy on the pass and the notches wouldn't fall into place. (isn't that what
he's complaining about?)
This is why I hate the reference (especially on a 2 meter duplexer) of Transmitter
and Receiver ports, as HPLR and LPHR always make sense, no matter frequency or
orientation of the repeater split.
As I
understood all the cavities are the same or are there two types?
Two types, HPLR and LPHR....
Also we
have made our only cables to join the units together using RG214. I’m
assuming all the cables should be � taking into account the velocity factor or
the cable?
The cabling might have to be changed to optimize the notch depths, but he needs
to get a little closer before worrying about that.
-----Original Message-----
From: [email protected]
[mailto:[email protected]]
On Behalf Of Kevin Custer
Sent: 03 June 2005 12:51
To: [email protected]
Subject: Re: [Repeater-Builder]
Help with Wacom WP-639 Duplexer
m1ror wrote:
Hello All
This is my second posting but I'm not sure if my first attempt made it
to the list.
I bought a set of what appear to be good condition Wacom WP-639 (144-
174Mhz) Duplexers originally tuned for 156Mhz. A friend has attempted
to align the filters but is having problem aligning the notch down to
145Mhz.
The problem he tells me is he can only get the notch down to 148Mhz
with the Invar rods pushed all the way in. He has made up new patching
loom and still the same result.
Has any body played with these and could offer any advice?
Have him swap the ports and try again, in other words, tune the duplexer
backwards from the way it is presently tuned using the opposite sides for the
receiver and transmitter. Minimum frequency separation happens with the
rods all the way in, which leads me to believe he is attempting to tune the
duplexer upside down, on the 'wrong' notch; there
are two notches, as explained below....
This article explains the basic principal for the Wacom WP-641 and 639 style
pass notch network. While specifically written about the 641, the effects
are the same for the 639, however, the notch depth won't be as deep with the
639 as what is stated in the article:
<http://www.repeater-builder.com/wacom/wacombpbrnotes.html>
Complete tuning directions are available from this page:
<http://www.repeater-builder.com/wacom/wp6xxVHFtuninginstructions.pdf>
If you still encounter difficulty after attempting the switch-a-roo, email us
back....
Kevin
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